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Date:   Fri, 21 Feb 2020 17:37:35 +0100
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Jiri Olsa <jolsa@redhat.com>, Jiri Olsa <jolsa@kernel.org>,
        linux-rt-users@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Juri Lelli <juri.lelli@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH] tracing: Fix trace entry and trace common fields for
 preempt_lazy_count
Message-ID: <20200221163735.53wt2fqoajcuj2js@linutronix.de>
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On 2020-02-21 11:21:52 [-0500], Steven Rostedt wrote:
…
> struct trace_entry {
> 	unsigned short		type;
> 	unsigned char		flags;
> 	unsigned char		preempt_count;
> 	int			pid;
> 	unsigned short		migrate_disable;
> 	unsigned short		padding;
> 	unsigned char		preempt_lazy_count;
> };
> 
> Which adds a ton of bloat.
…
> Why is migrate disable a short? Is there going to be more that 256
> nesting?

I don't think so. We go now and then > 10 and the trace file shows only
one digit. So I think that migrate_disable can use a byte field
here.
So we make migrate_disable and preempt_lazy_count a `char' type and keep
the `short' padding later on?

> -- Steve

Sebastian